https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77589
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to rguent...@suse.de from comment #4) > So DW_OP_GNU_implicit_ptr doesn't work here? Not sure > I understand how DW_OP_GNU_implicit_ptr works fully. That is, > > ... *(D#1 + 24) > DW_OP_GNU_implicit_ptr <span.0> + 0 > DW_OP_mul > > the examples in the specification always finish the dwarf expression > with DW_OP_GNU_implicit_ptr which wouldn't be the case here. No, it doesn't, for 2 reasons: 1) DW_OP_implicit_ptr (DWARF5) / DW_OP_GNU_implicit_ptr (GNU) is a DWARF location description op, so can't appear in the middle of DWARF expression, but has to appear on its own; it has a bias argument, so you can say that int a = 5; char *b = ((char *) &a) + 2; b has DW_AT_location DW_OP_GNU_implicit_ptr <a, 2>, but that is it; it is like DW_OP_reg* or DW_OP_stack_value that can't appear in the middle, and more like DW_OP_reg* which also has to appear on its own (or say combined through DW_OP_piece). 2) it doesn't give you the value, but the address of the referenced DIE. So, if 1) wasn't a problem, you'd need ... DW_OP_implicit_ptr <span.0> DW_OP_deref DW_OP_mul to get the value and multiply. I've proposed DW_OP_variable_value for this, will see if I get any feedback on that.
